Provide user source locators in Builder.error errors (bp #1618) (#1619)

* Provide user source locators in Builder.error errors (#1618)

Package chisel3 was not properly marked as an internal package so source
locators in reported errors would point to files like Bits.scala.

(cherry picked from commit baea2da8

)

* Resolve backport issues

Co-authored-by: Jack Koenig <koenig@sifive.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>